Fiberglass reinforced plastics have been widely accepted by industry. A particularly convenient mode of forming such reinforced plastics resides in the simultaneous spray application of liquid resin and cut or chopped fiberglass roving. Pursuant to this technique, a fiberglass cutter or chopper is mounted on a spray gun and fed with a continuous strand of roving which the chopper breaks into small pieces of predetermined length and discharges into the liquid spray from the spray gun, whereby the cut or chopped fibers are wetted and sprayed simultaneously with the resin into a mold or other forming vehicle.
One type of prior art device for cutting or breaking fiberglass roving into short fibers is shown in U.S. Pat. No. 3,011,257 to Bamberger. Combined resin spray guns and choppers are shown by way of example in the U.S. Pat. Nos. to Anderson 2,933,125, Nawalanic 2,995,173 and Scheinert 3,212,717. The structures shown in these patents are rather large, heavy and cumbersome. More compact arrangements of a spray gun and a detachable cutter assembly are shown in the U.S. Pat. Nos. to Jones 3,155,320 and Fram 3,491,443. However, even the latter arrangements are quite heavy and cumbersome.
In general, fiberglass choppers comprise a cutter rotor or roller carrying a plurality of blades and a back-up roller between which the roving is fed, the blades bearing on the back-up roller and chopping or breaking the roving as it passes between the two rollers. To facilitate the cutting action, the back-up roller is usually comprised of a resilient surface material. If the contact between the two rollers is too severe the back-up roller or the blades, or both, wear quickly and have to be replaced; on the other hand, if there is insufficient contact, cutting is incomplete or does not occur. To solve this problem, the Jones U.S. Pat. No. 3,155,320 provided a simple adjustment for the back-up roller but had the disadvantages of necessitating stopping the cutter to make the adjustment and requiring both hands of the operator to do so. The Fram U.S. Pat. No. 3,491,443 provided a complicated, self-adjusting feature for the rollers, but had a non-driven cutter roller structure which was used with a driven back up roller. Further, the adjustment of Fram's roller was difficult and required that the cutter be stopped since the adjustment was not easily accessible to the operator. In addition, Fram utilized a third roller engaging the back up roller to aid in feeding the roving to the blades, but no adjustment was provided to vary the contact with the feed roller as the back up roller wore down.
The blades of the cutter roller or rotor wear and need to be replaced, and such should be done easily and quickly. However, replacement could not be quickly accomplished in prior art cutters. For example, in the structure of Jones U.S. Pat. No. 3,155,320 a total of eight separate fasteners had to be removed and replaced in order to change the blades. Further, the cutter rotor was usually held in place on the chopper and could not be removed as a unit so that blade replacement was quite difficult and time consuming.
Cutting the roving into short segments is just one function of the cutter; it must also distribute the cut fibers in a pattern compatible with that of the spray gun so that the cut fibers are completely, or nearly completely, wetted by the resin spray. While some prior art attempts have been made to achieve such result, many have avoided or ignored the problem. For example, Bamberger U.S. Pat. No. 3,011,257 attempted to avoid the problem by using a separate cutter and, presumably, a separate spray gun. Of course Bamberger's approach had the disadvantage of greatly increased labor costs in that two separate operations had to be performed. Another approach to the problem was taken by Fram U.S. Pat. No. 3,491,443, wherein exhaust air from the air motor and additional air from the air line were used to hold the cut fibers together during discharge, with the pattern of the cut fibers upon discharge depending mainly upon the physical shape of the outlet nozzle. Scheinert U.S. Pat. No. 3,212,717 discloses the use of air for conveying cut roving, but not for controlling the discharge pattern thereof, somewhat similar to Bamberger.